Method for operating an automatic transmission

ABSTRACT

A method for operating an automatic transmission is provided. The method includes synchronizing a positive shifting element of the automatic transmission, braking the automatic transmission with a first non-positive shifting element of the automatic transmission, establishing a position of the positive shifting element, and increasing a pressure of fluid supplied to a second non-positive shifting element of the automatic transmission if the position of the positive shifting element is an intermediate position.

FIELD OF THE INVENTION

The present subject matter relates generally to automatic transmissions,such as nine-speed automatic transmissions.

BACKGROUND OF THE INVENTION

Automatic transmissions generally include at least one planetary gearset and a plurality of shift elements. The shift elements selectivelyengage components of the planetary gear sets in order to hinder orprevent rotation of the components. Selective actuation of the shiftelements adjusts the gear ratio of the automatic transmission and shiftsthe automatic transmission between its various gears.

Certain automatic transmissions include dog clutch shifting elements.During various gear shifts, the dog clutch is engaged or closed.Engaging the dog poses certain challenges. For example, the dog clutchis generally synchronized prior to engaging the dog clutch. When the dogclutch is synchronized, components of the dog clutch rotate at a commonspeed and may engage each other more easily. Conversely, such componentsmay grind against each other and be damaged if the dog clutch is engagedwhile the dog clutch is not synchronized. However, synchronizing the dogclutch can be difficult and/or time consuming. For example, a separatesynchronizing mechanism can consume valuable space within a transmissionand add to an overall cost of the automatic transmission.

Certain conditions can also hinder or prevent actuation of the dogclutch. For example, even when the dog clutch is synchronized, teeth ofthe dog clutch can butt against one another and hinder or preventengagement of the dog clutch. As another example, the teeth of the dogclutch can stick and hinder or prevent actuation of the dog clutch evenwhen the dog clutch is synchronized.

Accordingly, a method for synchronizing a dog clutch of an automatictransmission would be useful. In particular, a method for synchronizinga dog clutch of an automatic transmission that also includes steps forameliorating tooth butting and/or spline locking of the dog clutch wouldbe useful.

BRIEF DESCRIPTION OF THE INVENTION

The present subject matter provides a method for operating an automatictransmission. The method includes synchronizing a positive shiftingelement of the automatic transmission, braking the automatictransmission with a first non-positive shifting element of the automatictransmission, establishing a position of the positive shifting element,and increasing a pressure of fluid supplied to a second non-positiveshifting element of the automatic transmission if the position of thepositive shifting element is an intermediate position. Additionalaspects and advantages of the invention will be set forth in part in thefollowing description, or may be apparent from the description, or maybe learned through practice of the invention.

In a first exemplary embodiment, a method for operating an automatictransmission is provided. The automatic transmission has a plurality ofnon-positive shifting elements and at least one positive shiftingelement. The method includes synchronizing a first positive shiftingelement of the at least one positive shifting element, braking theautomatic transmission with a first non-positive shifting element of theplurality of non-positive shifting elements, and commanding the firstpositive shifting element of the at least one positive shifting elementto actuate from a disengaged configuration to an engaged configurationafter the step of synchronizing. A second non-positive shifting elementand a third non-positive shifting element of the plurality ofnon-positive shifting elements are in the engaged configuration at thestep of commanding. The method also includes establishing a position ofthe first positive shifting element of the at least one positiveshifting element after the step of commanding and increasing a pressureof fluid supplied to the second non-positive shifting element of theplurality of non-positive shifting elements if the position of the firstpositive shifting element of the at least one positive shifting elementis an intermediate position at the step of establishing.

In a second exemplary embodiment, a method for operating a nine-speedautomatic transmission is provided. The nine-speed automatictransmission includes a dog clutch A, a friction shifting element C, afriction shifting element D, and a friction shifting element E. Themethod includes synchronizing the dog clutch A, braking the automatictransmission with the friction shifting element C, and commanding thedog clutch A to actuate from a disengaged configuration to an engagedconfiguration after the step of synchronizing. The friction shiftingelement D and the friction shifting element E are in the engagedconfiguration at the step of commanding. Establishing a position of thedog clutch A after the step of commanding and increasing a pressure offluid supplied to the friction shifting element D if the position of thedog clutch A is an intermediate position at the step of establishing.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures.

FIG. 1 provides a schematic view of an automatic transmission accordingto an exemplary embodiment of the present subject matter.

FIG. 2 illustrates a table of an exemplary shifting scheme as may beused with the exemplary automatic transmission of FIG. 1.

FIG. 3 illustrates a method for operating an automatic transmissionaccording to an exemplary embodiment of the present subject matter.

FIGS. 4 and 5 illustrate plots of shifting element actuation for theexemplary automatic transmission of FIG. 1 during the exemplary methodof FIG. 3.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

FIG. 1 provides a schematic view of an automatic transmission 10according to an exemplary embodiment of the present subject matter.Automatic transmission 10 may be constructed or arranged in a similarmanner to the automatic transmission described in U.S. Pat. No.8,398,522 to Bauknecht et al., which is hereby incorporated by referencefor all purposes. Automatic transmission 10 may be used in any suitablevehicle. For example, automatic transmission 10 may be used in apassenger vehicle, such as a car, truck or sport utility vehicle (SUV).Automatic transmission 10 is configured for selectively adjusting a gearratio of automatic transmission 10, as will be understood by thoseskilled in the art, in order to provide a suitable mechanical advantageto propel the associated vehicle.

As may be seen in FIG. 1, automatic transmission 10 includes an inputshaft 12 and an output shaft 14. Input shaft 12 may be coupled to aturbine of a torque converter in order to link automatic transmission 10to a motor of an associated vehicle. Output shaft 14 may be coupled afront axle drive shaft of the associated vehicle. Automatic transmission10 may change gears in order to adjust the gear ratio between the motorand front axle drive shaft of the associated vehicle, as will beunderstood by those skilled in the art.

Automatic transmission 10 also includes four planetary gear sets: afirst planetary gear set 20; a second planetary gear set 22; a thirdplanetary gear set 24 and a fourth planetary gear set 26. In certainexemplary embodiments, as shown in FIG. 1, third and fourth planetarygear sets 24, 26 may be a Simpson planetary gear set, e.g., such thatthird and fourth planetary gear sets 24, 26 share a joint sun gear orsun gears of third and fourth planetary gear sets 24, 26 are coupled orfixed together. The sun gear of second planetary gear set 22 may alsoconstitute the ring gear of first planetary gear set 20, and planetgears of first and second planetary gear sets 20, 22 may be mounted to ajoint planet carrier that is also coupled or fixedly connected to thering gear of third planetary gear set 24. The planet carrier of thirdplanetary gear set 24 may also be coupled or fixedly connected to thering gear of fourth planetary gear set 26.

As may be seen in FIG. 1, automatic transmission 10 further includes aplurality of shifting elements. In particular, automatic transmission 10includes a plurality of non-positive shift elements and at least onepositive shifting element. The non-positive shift elements may be anysuitable type of non-positive shift elements. For example, thenon-positive shift elements may be multidisc friction shift elements orfriction bands. In the exemplary embodiment of FIG. 1, the non-positiveshifting elements includes a multidisc clutch B, a multidisc brake C, amultidisc brake D and a multidisc clutch E. The positive shiftingelements may also be any suitable type of positive shifting elements,e.g., that provide a form fit or torque proof connection. For example,the positive shifting elements may be dog clutches, dog brakes or clawclutches. In the exemplary embodiment of FIG. 1, the at least onepositive shifting element includes a dog clutch A and a dog clutch orbrake F. As used herein, the term “clutch” may refer to mechanism forcoupling or connecting two rotating components and the term “brake” mayrefer to a mechanism for coupling or connecting a rotating component toa non-rotating or static component.

The shifting elements of automatic transmission 10 selectively adjustbetween an open or disengaged configuration and a closed or engagedconfiguration. In the disengaged configuration, the shifting elements donot engage an associated component of the four planetary gear sets,e.g., and do not or negligibly interfere with rotation of the associatedcomponent of the four planetary gear sets relative to the shiftingelements. Conversely, in the engaged configuration, the shiftingelements engage the associated component of the four planetary gearsets, e.g., and hinder or prevent rotation of the associated componentof the four planetary gear sets relative to the shifting elements. Asmay be seen in FIG. 1, dog clutch A selectively connects or couplesinput shaft 12 to the sun gear of second planetary gear set 22 and thering gear of first planetary gear set 20. Multidisc clutch B selectivelyconnects or couples input shaft 12 to the sun gear of first planetarygear set 20. Multidisc brake C selectively connects or couples atransmission housing 16 to the sun gear of first planetary gear set 20.Multidisc brake D selectively connects or couples transmission housing16 to the ring gear of second planetary gear set 22. Multidisc clutch Eselectively connects or couples input shaft 12 to the planet carrier ofthird planetary gear set 24 and the ring gear of fourth planetary gearset 26. Dog clutch F selectively connects or couples transmissionhousing 16 to the sun gear of third and fourth planetary gear sets 24,26.

Automatic transmission 10 also includes an electronic control unit 28,an input speed sensor 30 and an output speed sensor 32. Electroniccontrol unit 28 is in operative communication with various components ofautomatic transmission 10, including input speed sensor 30 and outputspeed sensor 32, to regulate operation of automatic transmission 10.Electronic control unit 28 may include a memory and microprocessor, suchas a general or special purpose microprocessor operable to executeprogramming instructions or micro-control code associated with operatingof automatic transmission 10. The memory may represent random accessmemory such as DRAM, or read only memory such as ROM or FLASH.Alternatively, electronic control unit 28 may be constructed withoutusing a microprocessor, e.g., using a combination of discrete analogand/or digital logic circuitry (such as switches, amplifiers,integrators, comparators, flip-flops, AND gates, and the like) toperform control functionality instead of relying upon software.

Electronic control unit 28 may be mounted on an exterior of transmissionhousing 16. Electronic control unit 28 is in operative communicationwith solenoid valves of the shifting elements of automatic transmission10. Thus, electronic control unit 28 may selectively adjust the shiftingelements between the engaged configuration and the disengagedconfiguration, e.g., by selectively opening and closing the associatedsolenoid valves of the shifting elements. In such a manner, electroniccontrol unit 28 may shift automatic transmission 10 between gears duringoperation of automatic transmission 10, e.g., based at least in part onsignals from input speed sensor 30 and output speed sensor 32, as willbe understood by those skilled in the art.

Input speed sensor 30 is configured for measuring a speed, e.g.,rotations per minute (RPM), of input shaft 12. Input speed sensor 30 maybe positioned adjacent input shaft 12 or a turbine of an associatedtorque coupling. Input speed sensor 30 may be any suitable type ofsensor. For example, input speed sensor 30 may be a Hall effect sensor,an optical sensor, etc. Electronic control unit 28 may receive a signalfrom input speed sensor 30 corresponding to the speed of input shaft 12.

Output speed sensor 32 is configured for measuring a speed, e.g.,rotations per minute (RPM), of output shaft 14. Output speed sensor 32may be positioned adjacent output shaft 14. Output speed sensor 32 maybe any suitable type of sensor. For example, output speed sensor 32 maybe a Hall effect sensor, an optical sensor, etc. Electronic control unit28 may receive a signal from output speed sensor 32 corresponding to thespeed of output shaft 14.

FIG. 2 illustrates a table 200 of an exemplary shifting scheme as may beused with automatic transmission 10. As may be seen in FIG. 2, automatictransmission 10 includes nine forward gears and one reverse gear. Theforwards gears include: first gear “1”, second gear “2”, third gear “3”,fourth gear “4”, fifth gear “5”, sixth gear “6”, seventh gear “7”,eighth gear “8”, and ninth gear “9”. The reverse gear is labeled “R”. Intable 200, cells filled with “x” indicate the engaged configuration, andblank cells indicate the disengaged configuration. Thus, e.g., dogclutch A, multidisc brake D and dog clutch F are in the engagedconfiguration in first gear, and multidisc clutch B, multidisc brake Cand multidisc clutch E are in the disengaged configuration in firstgear. As another example, dog clutch A, multidisc brake C and dog clutchF are in the engaged configuration in second gear, and multidisc clutchB, multidisc brake D and multidisc clutch E are in the disengagedconfiguration in second gear. In the fourth gear, dog clutch A,multidisc clutch E and dog clutch F are in the engaged configuration. Itshould be understood that in certain exemplary embodiments, dog clutch Aneed not be in the engaged configuration to operate automatictransmission 10 in fourth gear. Thus, multidisc clutch E and dog clutchF may be the only shifting elements of automatic transmission 10 in theengaged configuration to operate automatic transmission 10 in fourthgear, in certain exemplary embodiments.

As discussed above, automatic transmission 10 includes nine forwardgears and one reverse gear. Thus, automatic transmission 10 is generallyreferred to as a “nine-speed automatic transmission.” However, it shouldbe understood that automatic transmission 10 is provided by way ofexample only and that the present subject matter may be used in or withany suitable automatic transmission. Thus, the present subject matter isnot intended to be limited to use with automatic transmission 10. As anexample, the present subject matter may be used in automatictransmissions having five forward gears, six forward gears, eightforward gears, etc.

FIG. 3 illustrates a method 300 for operating an automatic transmissionaccording to an exemplary embodiment of the present subject matter.Method 300 may be used in or with any suitable transmission. Forexample, method 300 may be used with automatic transmission 10 (FIG. 1).The electronic control unit 28 of automatic transmission 10 may beprogrammed or configured to implement method 300. Utilizing method 300,a positive shifting element of automatic transmission 10, such as dogclutch A or dog clutch F, may be synchronized and engaged, e.g., when anassociated vehicle is stopped or operating at slow speeds. Inparticular, method 300 may be used to synchronize and engage dog clutchA when an associated vehicle is stopped on a sloped surface, such as ahill.

FIGS. 4 and 5 illustrate plots of shifting element actuation forautomatic transmission 10 during method 300. FIG. 4 provides a plot ofshifting element actuation, including actuation of dog clutch A, withteeth of dog clutch A butting against one another during the actuationprocess. FIG. 5 provides a plot of shifting element actuation, includingactuation of dog clutch A, with teeth of dog clutch A locking againstone another during the actuation process. Method 300 is described ingreater detail below with reference to FIGS. 4 and 5.

In FIGS. 4 and 5, lines labeled “current of C”, “current of D” and“current of E” correspond to a command current supplied to a respectivesolenoid valve of multidisc brake C, multidisc brake D and multidiscclutch E. Electronic control unit 28 may selectively adjust the currentsupplied to the respective solenoid valve of multidisc brake C,multidisc brake D and multidisc clutch E as shown in FIGS. 4 and 5. Theline labeled “position of A” corresponds to a measured or detectedposition for dog clutch A, with the lower position corresponding to thedisengaged configuration, the higher position corresponding to theengaged configuration, and the middle position corresponding to anintermediate position between the engaged and disengaged configurations.Dog clutch A may be in the intermediate position, e.g., when teeth ofdog clutch A are butting against one another or when teeth of dog clutchA are locked together. The line labeled “line pressure” corresponds to apressure supplied to shifting elements of automatic transmission 10,such as dog clutch A, multidisc brake C, multidisc brake D and multidiscclutch E. Electronic control unit 28 may selectively increase thecommand line pressure as shown in FIGS. 4 and 5, e.g., by selectivelyincreasing an idle speed of a motor coupled to input shaft 12. The line“input speed” corresponds to a measured or detected speed of input shaft12, e.g., from input speed sensor 30, and the line “output speed”corresponds to a measured or detected speed of output shaft 14, e.g.,from output speed sensor 32. In FIGS. 4 and 5, the illustrated commandcurrent supplied to the respective solenoid valve of multidisc brake C,multidisc brake D and multidisc clutch E may also correspond orcorrelate to the fluid pressure supplied to such shifting elements.

At step 310, a positive shifting element of automatic transmission 10,such as dog clutch A, is synchronized in order to permit the positiveshifting element to be engaged. Dog clutch F may engaged prior tostarting method 300, e.g., before step 310. As an example, during step310, a friction shifting element of automatic transmission 10 may beclosed. In particular, multidisc brake D may be closed at step 310, asmay be seen in FIGS. 4 and 5. Electronic control unit 28 may open asolenoid valve of multidisc brake D in order to close multidisc brake Dat step 310. In particular, as may be seen in FIGS. 4 and 5, electroniccontrol unit 28 may first open the solenoid valve of multidisc brake Dto a first position by pulsing the current supplied to multidisc brake Dto a first level L1, e.g., in order to fill any void(s) within a line tomultidisc brake D with fluid. Electronic control unit 28 may thendecrease the current supplied to the solenoid valve of multidisc brake Dand increase the current supplied to the solenoid valve of multidiscbrake D along a first actuating trajectory T1 until the current suppliedto the solenoid valve of multidisc brake D reaches an actuation value A1and the multidisc brake D is in the actuated configuration. In such amanner, multidisc brake D may be closed at step 310 in order to assistwith synchronizing dog clutch A.

In addition, a second friction shifting element of automatictransmission 10 may be brought to an engaged configuration of the secondfriction shifting element at step 310. For example, multidisc clutch Emay be brought to an engaged configuration of multidisc clutch E at step310, as may be seen in FIGS. 4 and 5. Electronic control unit 28 mayopen a solenoid valve of multidisc clutch E in order to bring multidiscclutch E to its engaged configuration at step 310. In particular, as maybe seen in FIGS. 4 and 5, electronic control unit 28 may first open thesolenoid valve of multidisc clutch E to a first position by pulsing thecurrent supplied to multidisc clutch E to a second level L2, e.g., inorder to fill any void(s) within a line to multidisc clutch E withfluid. Electronic control unit 28 may then decrease the current suppliedto the solenoid valve of multidisc clutch E and increase the currentsupplied to the solenoid valve of multidisc clutch E along a secondactuating trajectory T2 such that the multidisc clutch E is positionedat the engaged configuration of multidisc clutch E. In such a manner,multidisc clutch E may be brought to the engaged configuration ofmultidisc clutch E at step 310. As may be seen in FIGS. 4 and 5,multidisc clutch E may be brought to the engaged configuration ofmultidisc clutch E after beginning to close multidisc brake D to theactuated configuration during step 310.

Step 310 may assist with reducing a speed differential between rotatingcomponents of the positive shifting element of automatic transmission10. For example, step 310 may assist with reducing a speed differentialbetween rotating components of dog clutch A. Thus, step 310 may assistwith synchronizing dog clutch A in order to assist with actuating dogclutch A from the disengaged configuration to the engaged configuration.In particular, by closing multidisc brake D and bringing multidiscclutch E to its engaged configuration, dog clutch A may be synchronizedand actuated to the engaged configuration.

At step 310, automatic transmission 10 may also be operated such that anoutput speed of automatic transmission 10 is less than a thresholdoutput speed. As an example, electronic control unit 28 may receivespeed measurements of output shaft 14 from output speed sensor 32 tomeasure the output speed of automatic transmission 10 at step 310. Thethreshold output speed may be any suitable speed. For example, thethreshold output speed may be zero rotations per minute, no greater thanone thousand rotations per minute, no greater than five hundredrotations per minute, etc. Thus, a vehicle associated with automatictransmission 10 may be stopped or moving slowly at step 310.

At step 320, automatic transmission 10, e.g., and an associated vehicle,are braked with a friction shifting element of automatic transmission10. For example, a third friction shifting element of automatictransmission 10 may be closed at step 320. In particular, multidiscbrake C may be closed at step 320, as may be seen in FIGS. 4 and 5.Electronic control unit 28 may open a solenoid valve of multidisc brakeC in order to close multidisc brake C at step 320. In particular, as maybe seen in FIGS. 4 and 5, electronic control unit 28 may first open thesolenoid valve of multidisc brake C to a first position by pulsing thecurrent supplied to multidisc brake C to a third level L3, e.g., inorder to fill any void(s) within a line to multidisc brake C with fluid.Electronic control unit 28 may then decrease the current supplied to thesolenoid valve of multidisc brake C and increase the current supplied tothe solenoid valve of multidisc brake C along a third actuatingtrajectory T3 in order to adjust the multidisc brake C to the actuatedconfiguration. In such a manner, multidisc brake C may be closed at step320 in order to assist with braking automatic transmission 10 and/or avehicle associated with automatic transmission 10.

By braking automatic transmission 10 and/or the vehicle associated withautomatic transmission 10 at step 320, a vehicle associated withautomatic transmission 10 may be hindered or prevented from rollingbackwards. Thus, while on a hill or other sloped surface, multidiscbrake C may brake automatic transmission 10 and/or the vehicleassociated with automatic transmission 10 at step 320. In such a manner,multidisc brake C may limit or prevent damage to a positive shiftingelement of automatic transmission 10, e.g., while the positive shiftingelement of automatic transmission 10 is shifted to the engagedconfiguration.

At step 330, a positive shifting element of automatic transmission 10 iscommanded to close or actuate to the engaged configuration. As anexample, dog clutch A may be commanded to actuate to from the disengagedconfiguration to the engaged configuration at step 330, e.g., after dogclutch A is synchronized during step 310. In particular, electroniccontrol unit 28 may open a solenoid valve of dog clutch A such that apressure of fluid supplied to dog clutch A is increased in order tocommand dog clutch A to adjust to the engaged configuration at step 330,as shown in FIGS. 4 and 5.

At step 340, a position of the positive shifting element of automatictransmission 10 is determined or established. Electronic control unit 28may determine the position of dog clutch A at step 340. Any suitablemethod or mechanism may be used to determine or establish that positionof dog clutch A at step 340. As an example, electronic control unit 28may utilize the method described in U.S. Pat. No. 8,812,200 of Novak,which is hereby incorporated by reference for all purposes, to determinethe position of dog clutch A at step 340. As another example, electroniccontrol unit 28 may utilize a pressure difference across an actuatingpiston of the dog clutch A to determine the position of the position ofdog clutch A at step 340, as will be understood by those skilled in theart.

If the position of the positive shifting element is in an intermediateposition at step 340, a pressure of fluid supplied to a non-positiveshifting element of automatic transmission 10 is increased at step 350.For example, a pressure of fluid supplied to multidisc brake D may beincreased at step 350, as may be seen in FIGS. 4 and 5. Electroniccontrol unit 28 may open a solenoid valve of multidisc brake D in orderto increase the pressure of fluid supplied to brake D at step 350. Inparticular, as may be seen in FIGS. 4 and 5, electronic control unit 28may further open the solenoid valve of multidisc brake D to a secondposition by increasing the current supplied to multidisc brake D to athird actuation value A3 along a fourth actuating trajectory T4 in orderto increase the pressure of fluid supplied to multidisc brake D at step350. Multidisc brake C may continue brake automatic transmission 10and/or the vehicle associated with automatic transmission 10 during step350. As may be seen in FIGS. 4 and 5, multidisc clutch E may also beopened at step 350, e.g., by opening decreasing the current supplied tothe solenoid valve of multidisc clutch E along the fifth actuatingtrajectory T5.

During step 350, a rotational speed differential between torquecouplings of dog clutch A may continue to increase. Thus, if teeth ofdog clutch A are butting against one another and dog clutch A is stuckin the intermediate position, the rotational speed differential betweentorque couplings of dog clutch A may be increased at step 350 in orderto eliminate the tooth butt condition of dog clutch A. As shown in FIG.4, dog clutch A may be actuated from the intermediate position to theengaged configuration when the tooth butt condition of dog clutch A iseliminated at step 350. With dog clutch A synchronized and in theengaged configuration, multidisc brake C, multidisc brake D andmultidisc clutch E may be opened to the disengaged configuration at step380, as shown in FIGS. 4 and 5.

If the position of the positive shifting element is in not theintermediate position at step 340, dog clutch A is in the engagedconfiguration. Thus, multidisc brake C, multidisc brake D and multidiscclutch E may be opened at step 380, e.g., by reducing current suppliedto solenoid valves of multidisc brake C, multidisc brake D and multidiscclutch E. In addition, automatic transmission 10 may be shifted to firstgear or the reverse gear with dog clutch A in the engaged configurationafter step 380.

At step 360, the position of the positive shifting element of automatictransmission 10 is again determined or established. If the position ofthe positive shifting element is still the intermediate position, apressure of fluid supplied to a non-positive shifting element ofautomatic transmission 10 may be pulsed at step 370. For example, apressure of fluid supplied to multidisc brake D may be pulsed at step370, as may be seen in FIG. 5. Electronic control unit 28 maysuccessively open and close a solenoid valve of multidisc brake D inorder to pulse the pressure of fluid supplied to brake D at step 370. Ifincreasing the pressure of fluid supplied to multidisc brake D at step350 does not permit or result in dog clutch A shifting to the engagedconfiguration, teeth of dog clutch A may be sticking. By pulsing thepressure of fluid supplied to multidisc brake D, the sticking may beovercome and dog clutch A may shift to the engaged configuration. Insuch a manner, spline lock condition of dog clutch A may be eliminatedor overcome. The pressure of fluid supplied to the non-positive shiftingelement of automatic transmission 10 may be pulsed any suitable numbersof times at step 370. For example, the non-positive shifting element ofautomatic transmission 10 may be pulsed once, two times, three times,four times, five times, or more.

As may be seen in FIG. 5, multidisc clutch E may also be closed at step370, e.g., in order to assist with overcoming the spline lock conditionof dog clutch A. In particular, electronic control unit 28 may open thesolenoid valve of multidisc clutch E by increasing the current suppliedto the solenoid valve of multidisc clutch E to a fourth level A4.Multidisc brake C may also stop braking automatic transmission 10 and/orthe vehicle associated with automatic transmission 10 during step 370.

It should be understood that while described in the context of automatictransmission 10, method 300 may be used to synchronize and engage apositive shifting element in any suitable transmission. In addition,while described in the context of synchronizing and engaging dog clutchA, method 300 may be used to detect synchronize and engage dog clutch Aof automatic transmission 10, in alternative exemplary embodiments.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A method for operating an automatic transmission,the automatic transmission having a plurality of non-positive shiftingelements and at least one positive shifting element, the methodcomprising: synchronizing a first positive shifting element of the atleast one positive shifting element; braking the automatic transmissionwith a first non-positive shifting element of the plurality ofnon-positive shifting elements; commanding the first positive shiftingelement of the at least one positive shifting element to actuate from adisengaged configuration to an engaged configuration after said step ofsynchronizing, a second non-positive shifting element and a thirdnon-positive shifting element of the plurality of non-positive shiftingelements being in the engaged configuration at said step of commanding;establishing a position of the first positive shifting element of the atleast one positive shifting element after said step of commanding; andincreasing a pressure of fluid supplied to the second non-positiveshifting element of the plurality of non-positive shifting elements ifthe position of the first positive shifting element of the at least onepositive shifting element is an intermediate position at said step ofestablishing.
 2. The method of claim 1, further comprising decreasing apressure of fluid supplied to the third non-positive shifting element ofthe plurality of non-positive shifting elements if the position of thefirst positive shifting element of the at least one positive shiftingelement is the intermediate position at said step of establishing. 3.The method of claim 1, further comprising determining the position ofthe first positive shifting element of the at least one positiveshifting element after said step of increasing and pulsing the pressureof fluid supplied to the second non-positive shifting element of theplurality of non-positive shifting elements if the position of the firstpositive shifting element of the at least one positive shifting elementis the intermediate position at said step of determining.
 4. The methodof claim 3, further comprising opening the third non-positive shiftingelement of the plurality of non-positive shifting elements if theposition of the first positive shifting element of the at least onepositive shifting element is the intermediate position at said step ofestablishing and closing the third non-positive shifting element of theplurality of non-positive shifting elements if the position of the firstpositive shifting element of the at least one positive shifting elementis the intermediate position at said step of determining.
 5. The methodof claim 4, wherein the position of the first positive shifting elementof the at least one positive shifting element is an engaged positionafter said steps of pulsing and closing.
 6. The method of claim 3,further comprising adjusting the first non-positive shifting element ofthe plurality of non-positive shifting elements to a disengagedconfiguration during said step of pulsing.
 7. The method of claim 3,wherein said step of pulsing comprises sequentially reducing andboosting the pressure of fluid supplied to the second non-positiveshifting element of the plurality of non-positive shifting elements atleast three times.
 8. The method of claim 1, wherein a second positiveshifting element of the at least one positive shifting element is in anengaged position at said step of commanding.
 9. The method of claim 1,wherein increasing a line pressure of the automatic transmissioncomprises increasing an idle speed of a motor a vehicle associated withthe automatic transmission during said step of synchronizing.
 10. Themethod of claim 1, wherein a vehicle associated with the automatictransmission does not roll backwards during said steps of synchronizing,braking, commanding, establishing and increasing.
 11. A method foroperating a nine-speed automatic transmission, the nine-speed automatictransmission including a dog clutch A, a friction shifting element C, afriction shifting element D, and a friction shifting element E, themethod comprising: synchronizing the dog clutch A; braking the automatictransmission with the friction shifting element C; commanding the dogclutch A to actuate from a disengaged configuration to an engagedconfiguration after said step of synchronizing, the friction shiftingelement D and the friction shifting element E being in the engagedconfiguration at said step of commanding; establishing a position of thedog clutch A after said step of commanding; and increasing a pressure offluid supplied to the friction shifting element D if the position of thedog clutch A is an intermediate position at said step of establishing.12. The method of claim 11, further comprising decreasing a pressure offluid supplied to the friction shifting element E if the position of thedog clutch A is the intermediate position at said step of establishing.13. The method of claim 11, further comprising determining the positionof the first positive shifting element of the at least one positiveshifting element after said step of increasing and pulsing the pressureof fluid supplied to the friction shifting element D if the position ofthe dog clutch A is the intermediate position at said step ofdetermining.
 14. The method of claim 13, further comprising opening thefriction shifting element E if the position of the dog clutch A is theintermediate position at said step of establishing and closing thefriction shifting element E if the position of the dog clutch A is theintermediate position at said step of determining.
 15. The method ofclaim 14, wherein the position of the dog clutch A is an engagedposition after said steps of pulsing and closing.
 16. The method ofclaim 13, further comprising adjusting the friction shifting element Cto a disengaged configuration during said step of pulsing.
 17. Themethod of claim 13, wherein said step of pulsing comprises sequentiallyreducing and boosting the pressure of fluid supplied to the frictionshifting element D at least three times.
 18. The method of claim 11,wherein a dog clutch F of the automatic transmission is in an engagedposition at said step of commanding.
 19. The method of claim 11, whereinincreasing a line pressure of the automatic transmission comprisesincreasing an idle speed of a motor a vehicle associated with theautomatic transmission during said step of synchronizing.
 20. The methodof claim 11, wherein a vehicle associated with the automatictransmission does not roll backwards during said steps of synchronizing,braking, commanding, establishing and increasing.